• Journal of Chest Surgery
• /
• v.53 no.5
• /
• pp.306-309
• /
• 2020

A 59-year-old man presented for possible durable ventricular assist device (VAD) implantation. He had previously been diagnosed with congenitally corrected transposition of the great arteries, a ventricular septal defect, an atrial septal defect, pulmonary valve stenosis, and aortic valve regurgitation. In the previous 22 years, he had undergone palliative cardiac surgery 3 times. VAD implantation as a bridge to transplantation was planned. Owing to severe adhesions, mesocardia, a left ascending aorta, and moderate aortic regurgitation, we performed VAD implantation and aortic valve closure via a dual left thoracotomy and partial sternotomy.

• The Journal of the Acoustical Society of Korea
• /
• v.36 no.5
• /
• pp.345-352
• /
• 2017

We propose a methods which is reducing direction estimation error of sound source in the reverberant and noisy environments. The proposed algorithm divides speech signal into voice and unvoice using VAD. We estimate the direction of source when current frame is voiced. TDOA (Time-Difference of Arrival) between microphone array using the GCC-PHAT (Generalized Cross Correlation with Phase Transform) method will be estimated in that frame. Then, we compare the peak value of cross-correlation of two signals applied to estimated time-delay with other time-delay in time-table in order to improve the accuracy of source location. If the angle of current frame is far different from before and after frame in successive voiced frame, the angle of current frame is replaced with mean value of the estimated angle in before and after frames.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.1
• /
• pp.61-69
• /
• 1998

Vapor Axial Deposition (VAD), one of optical fiber preform fabrication processes, is performed by deposition of submicron-size silica particles that are synthesized by combustion of raw chemical materials. In this study, flow field is assumed to be a forced uniform flow perpendicularly impinging on a rotating disk. Similarity solutions obtained in our previous study are utilized to solve the particle transport equation. The particles are approximated to be in a polydisperse state that satisfies a lognormal size distribution. A moment model is used in order to predict distributions of particle number density and size simultaneously. Deposition of the particles on the disk is examined considering convection, Brownian diffusion, thermophoresis, and coagulation with variations of the forced flow velocity and the disk rotating velocity. The deposition rate and the efficiency directly increase as the flow velocity increases, resulting from that the increase of the forced flow velocity causes thinner thermal and diffusion boundary layer thicknesses and thus causes the increase of thermophoretic drift and Brownian diffusion of the particles toward the disk. However, the increase of the disk rotating speed does not result in the direct increase of the deposition rate and the deposition efficiency. Slower flow velocity causes extension of the time scale for coagulation and thus yields larger mean particle size and its geometric standard deviation at the deposition surface. In the case of coagulation starting farther from the deposition surface, coagulation effects increases, resulting in the increase of the particle size and the decrease of the deposition rate at the surface.

• Journal of Korea Multimedia Society
• /
• v.4 no.1
• /
• pp.56-66
• /
• 2001

The spectral subtraction algorithm using a criterion based on the human perception has been recently developed. The speech processed with Virag's algorithm sounds more pleasant to a human listener than those obtained by the classical methods. However, Virag's algorithm requires a robust voice activity detector (VAD). In the ESS (extended spectral subtraction) algorithm without VAD, the residual noise becomes more noticeable as the SNR decrease. In this paper we propose a new speech enhancement method, the combination of Wiener filter and spectral subtraction based on noise masking characteristics in the human auditory system. There is no need of VAD because the noise can be successively updated even during speech activity using Wiener filter. The adjustment of the subtraction parameter based on the masking threshold makes the residual noise inaudible. The proposed method has been compared with conventional spectral subtraction algorithms. Objective and subjective evaluation of the proposed system is performed with several noise types having different time-frequency distributions. The application of objective measures, the study of the speech spectrograms, as well as subjective listening tests, confirm that the enhanced speech with proposed algorithm is more pleasant to a human listener.

• Journal of Environmental Science International
• /
• v.18 no.3
• /
• pp.333-343
• /
• 2009

This study presents the analysis of an atmospheric flow around a single-doppler radar located in a pseudo-site. The use of a doppler radar in meteorological field of wind engineering has become widespread over the last several decades, but it has generally been recognized that the single-Doppler radar yields only one single velocity component - the radial velocity($V_r$) so that some additional hypotheses or simplifications must be necessary to get proper wind forecast. Therefore, in order to get an accurate radial velocity($V_r$) in this study, the existing methods such as VAD(Velocity Azimuth Display) and VARD(Velocity Area Display) are reformulated and applied to match the previous study(Waldteufel and Corbin), which have been an important indicator for retrieving a radar velocity. The results presented in this study include the results from different assessment methods in a peudo-site of different wind fields. Unless the existing method can consider the proper decomposition of radial velocity in the real site, then authors suggest an appropriate curve-fitting to decrease the uncertainty errors by changing a grid adaptation rate or applying a weighting function with respect to the wind angle. It is concluded that provided properly formulated fitting function are used, the wind retrieval from the Doppler radar using VAD and VARD methods can be a viable tool for use in wind engineering problems searching for the wind resources.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.5
• /
• pp.1671-1678
• /
• 1996

In external chemical vapor deposition processes including VAD and OVD the distribution of flame-synthesized silica particles is determined by heat and mass transfer limitations to particle formation. Combustion gas flow velocities are such that the particle diffusion time scale is longer than that of gas flow convection in the zone of particle formation. The consequence of these effects is that the particles formed tend to remain along straight smooth flow stream lines. Silica particles are formed due to oxidation and hydrolysis. In the hydrolysis, the particles are formed in diffuse bands and particle formation thus requires the diffusion of SiCl$\_$4/ toward CH$\_$4//O$\_$2/ combustion zone to react with H$\_$2/O diffusing away from these same zones on the torch face. The conversion kinetics of hydrolysis is fast compared to diffusion and the rate of conversion is thus diffusion-limited. In the language of combustion, the hydrolysis occurs as a Burke-Schumann process. In selected conditions, reaction zone shape and temperature distributions predicted by the Burke-Schumann analysis are introduced and compared with experimental data available. The calculated centerline temperatures inside the reaction zone agree well with the data, but the calculated values outside the reaction zone are a little higher than the data since the analysis does not consider diffusion in the axial direction and mixing of the combustion products with ambient air. The temperatures along the radial direction agree with the data near the centerline, but gradually diverge from the data as the distance is away from the centerline. This is caused by the convection in the radial direction, which is not considered in the analysis. Spatial distribution of silica particles are affected by convection and diffusion, resulting in a Gaussian form in the radial direction.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.4
• /
• pp.286-292
• /
• 2003

Voice activity detection (VAD) is a process that separates the noise region from silence or noise region of input speech signal. Since unvoiced consonant signals have very similar characteristics to those of noise signals, it may result in serious distortion of unvoiced consonants, or in erroneous noise estimation to can out VAD without paying special attention on unvoiced consonants. In this paper, we propose a method to extract in an explicit way the boundaries between unvoiced consonant and noise in fluent speech so that more exact VAD could be performed. The proposed method is based on histogram in frequency domain which was successfully used by Hirsch for noise estimation, and a1so on similarity measure of frequency components between adjacent frames, To evaluate the performance of the proposed method, experiments on unvoiced consonant boundary extraction was performed on seven kinds of noisy speech signals of 10 ㏈ and 15 ㏈ SNR respectively.

• Journal of Trauma and Injury
• /
• v.20 no.2
• /
• pp.101-105
• /
• 2007

Purpose: This study aimed to find any difference in the clinical or the anatomical findings of vertebral artery dissection (VAD) between the trauma and the non-trauma groups. Methods: We retrospectively reviewed the clinical data and radiologic images of VAD patients. We compared data on symptoms, neurologic deficit, National institutes of health stroke scale (NIHSS) at admission, Rankin score (RS) at admission and discharge, and radiological findings including anatomical features, between the trauma and the non-trauma groups. Results: From January 1997 to May 2006, 42 patients were enrolled and 13 patients (31%) had a history of earlier trauma. Focal neurologic deficit (trauma group 11/13 vs. non-trauma group 11/29), cerebral stroke (10/13 vs. 9/29), and extradural lesions of dissection (6/13 vs. 3/28) were more common in the trauma group than non-trauma group (p=0.007, p=0.017, p=0.018, respectively) and NIHSS at admission and discharge were significantly higher (p=0.012, p=0.001, respectively). Dissecting aneurysms were less frequent in the trauma group (2/13 vs. 19/29, p=0.006). Subarachnoid hemorrhage and unfavorable prognostic value (Rankin score at discharge ${\geq}$ 2) showed no differences between the groups (p=0.540, p=0.267, respectively). Conclusion: In VAD patients after trauma, focal neurologic deficit due to ischemic stroke and a steno-occlusive pattern are more frequent than they are in non-trauma patients. The location of dissection was most frequent at the extradural vertebral artery in the trauma group. NIHSS was higher in the trauma groups but the incidence of an unfavorable prognostic value (RS ${\geq}$ 2) was not significantly different between the groups.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.12
• /
• pp.1744-1749
• /
• 2013

Acoustic feedback is perceived as whistling or howling, which is a major complaint of hearing-aids users. Acoustic feedback cancellation is important in hearing-aids because acoustic feedback degrades performance of the hearing aid device by reducing maximum insertion gain. Adaptive systems for estimate acoustic feedback path and feedback suppression algorithms have been proposed in order to solve this problem. A typical feedback cancellation algorithm is LMS(least mean squares) because of its computational efficiency. However it has problem of convergence performance in high correlated input signal. In this paper, we propose a new variable step-size normalized LMS(least mean squares) algorithm using VAD(voice activity detection) to overcome the limitation of the LMS algorithm. The VAD algorithm is GSAP(global speech absence probability) and the feedback cancellation algorithm is normalized LMS. The proposed algorithm applies different step-size between voice and non-voice using VAD, for high stability, fast convergence speed and low misalignment when correlated inputs, such as speech. The result of simulation with white noise mixed speech signal, the proposed algorithm shows high performance then traditional algorithm in terms of stability, convergence speed and misalignment.

• Korean Journal of Adult Nursing
• /
• v.28 no.2
• /
• pp.169-179
• /
• 2016

Purpose: The purpose of this study was to investigate the effects of simulation-based training (SBT) for basic life support (BLS) utilizing video-assisted debriefing (VAD) about non-technical skills (NTSs) and technical skills (TSs). The goal of the proposed study is the evaluation of a teaching method about the correct application of cardiopulmonary resuscitation (CPR). Methods: The study design was a control group pre- and post-test non-synchronized experimental design. The sample included twelve teams of 36 nursing students. Both the experimental and the control groups received the SBT for BLS. Only the experimental groups received VAD where as the control groups had a verbal debriefing. Raters who used checklists for TSs and NTSs evaluated both groups. Data were analyzed by the SPSS 20.0 using Cronbach's ${\alpha}$, Intraclass Correlation Coefficient (ICC), Mann-Whitney U test and Willcoxon signed rank test. Results: The experimental groups scored higher than the control groups in both TSs (p=.004) and the NTSs (p=.008). Conclusion: The findings of this study suggest that NTSs are an important factor that lead CPR successfully, so VAD can be used as an efficient teaching-learning strategy in the SBT for BLS for nursing students and nurses.